import {
  Color,
  LinearFilter,
  MathUtils,
  Matrix4,
  Mesh,
  PerspectiveCamera,
  Plane,
  RGBFormat,
  ShaderMaterial,
  UniformsUtils,
  Vector3,
  Vector4,
  WebGLRenderTarget
} from 'three'

class Reflector extends Mesh {
  constructor (geometry, options = {}) {
    super(geometry)

    this.type = 'Reflector'

    const scope = this

    const color = (options.color !== undefined) ? new Color(options.color) : new Color(0x7F7F7F)
    const textureWidth = options.textureWidth || 512
    const textureHeight = options.textureHeight || 512
    const clipBias = options.clipBias || 0
    const shader = options.shader || Reflector.ReflectorShader

    //

    const reflectorPlane = new Plane()
    const normal = new Vector3()
    const reflectorWorldPosition = new Vector3()
    const cameraWorldPosition = new Vector3()
    const rotationMatrix = new Matrix4()
    const lookAtPosition = new Vector3(0, 0, -1)
    const clipPlane = new Vector4()

    const view = new Vector3()
    const target = new Vector3()
    const q = new Vector4()

    const textureMatrix = new Matrix4()
    const virtualCamera = new PerspectiveCamera()

    const parameters = {
      minFilter: LinearFilter,
      magFilter: LinearFilter,
      format: RGBFormat
    }

    const renderTarget = new WebGLRenderTarget(textureWidth, textureHeight, parameters)

    if (!MathUtils.isPowerOfTwo(textureWidth) || !MathUtils.isPowerOfTwo(textureHeight)) {
      renderTarget.texture.generateMipmaps = false
    }

    const material = new ShaderMaterial({
      uniforms: UniformsUtils.clone(shader.uniforms),
      fragmentShader: shader.fragmentShader,
      vertexShader: shader.vertexShader
    })

    material.uniforms.tDiffuse.value = renderTarget.texture
    material.uniforms.color.value = color
    material.uniforms.textureMatrix.value = textureMatrix

    this.material = material

    this.onBeforeRender = function (renderer, scene, camera) {
      reflectorWorldPosition.setFromMatrixPosition(scope.matrixWorld)
      cameraWorldPosition.setFromMatrixPosition(camera.matrixWorld)

      rotationMatrix.extractRotation(scope.matrixWorld)

      normal.set(0, 0, 1)
      normal.applyMatrix4(rotationMatrix)

      view.subVectors(reflectorWorldPosition, cameraWorldPosition)

      // Avoid rendering when reflector is facing away

      if (view.dot(normal) > 0) return

      view.reflect(normal).negate()
      view.add(reflectorWorldPosition)

      rotationMatrix.extractRotation(camera.matrixWorld)

      lookAtPosition.set(0, 0, -1)
      lookAtPosition.applyMatrix4(rotationMatrix)
      lookAtPosition.add(cameraWorldPosition)

      target.subVectors(reflectorWorldPosition, lookAtPosition)
      target.reflect(normal).negate()
      target.add(reflectorWorldPosition)

      virtualCamera.position.copy(view)
      virtualCamera.up.set(0, 1, 0)
      virtualCamera.up.applyMatrix4(rotationMatrix)
      virtualCamera.up.reflect(normal)
      virtualCamera.lookAt(target)

      virtualCamera.far = camera.far // Used in WebGLBackground

      virtualCamera.updateMatrixWorld()
      virtualCamera.projectionMatrix.copy(camera.projectionMatrix)

      // Update the texture matrix
      textureMatrix.set(
        0.5, 0.0, 0.0, 0.5,
        0.0, 0.5, 0.0, 0.5,
        0.0, 0.0, 0.5, 0.5,
        0.0, 0.0, 0.0, 1.0
      )
      textureMatrix.multiply(virtualCamera.projectionMatrix)
      textureMatrix.multiply(virtualCamera.matrixWorldInverse)
      textureMatrix.multiply(scope.matrixWorld)

      // Now update projection matrix with new clip plane, implementing code from: http://www.terathon.com/code/oblique.html
      // Paper explaining this technique: http://www.terathon.com/lengyel/Lengyel-Oblique.pdf
      reflectorPlane.setFromNormalAndCoplanarPoint(normal, reflectorWorldPosition)
      reflectorPlane.applyMatrix4(virtualCamera.matrixWorldInverse)

      clipPlane.set(reflectorPlane.normal.x, reflectorPlane.normal.y, reflectorPlane.normal.z, reflectorPlane.constant)

      const projectionMatrix = virtualCamera.projectionMatrix

      q.x = (Math.sign(clipPlane.x) + projectionMatrix.elements[8]) / projectionMatrix.elements[0]
      q.y = (Math.sign(clipPlane.y) + projectionMatrix.elements[9]) / projectionMatrix.elements[5]
      q.z = -1.0
      q.w = (1.0 + projectionMatrix.elements[10]) / projectionMatrix.elements[14]

      // Calculate the scaled plane vector
      clipPlane.multiplyScalar(2.0 / clipPlane.dot(q))

      // Replacing the third row of the projection matrix
      projectionMatrix.elements[2] = clipPlane.x
      projectionMatrix.elements[6] = clipPlane.y
      projectionMatrix.elements[10] = clipPlane.z + 1.0 - clipBias
      projectionMatrix.elements[14] = clipPlane.w

      // Render

      renderTarget.texture.encoding = renderer.outputEncoding

      scope.visible = false

      const currentRenderTarget = renderer.getRenderTarget()

      const currentXrEnabled = renderer.xr.enabled
      const currentShadowAutoUpdate = renderer.shadowMap.autoUpdate

      renderer.xr.enabled = false // Avoid camera modification
      renderer.shadowMap.autoUpdate = false // Avoid re-computing shadows

      renderer.setRenderTarget(renderTarget)

      renderer.state.buffers.depth.setMask(true) // make sure the depth buffer is writable so it can be properly cleared, see #18897

      if (renderer.autoClear === false) renderer.clear()
      renderer.render(scene, virtualCamera)

      renderer.xr.enabled = currentXrEnabled
      renderer.shadowMap.autoUpdate = currentShadowAutoUpdate

      renderer.setRenderTarget(currentRenderTarget)

      // Restore viewport

      const viewport = camera.viewport

      if (viewport !== undefined) {
        renderer.state.viewport(viewport)
      }

      scope.visible = true
    }

    this.getRenderTarget = function () {
      return renderTarget
    }
  }
}

Reflector.prototype.isReflector = true

Reflector.ReflectorShader = {

  uniforms: {

    color: {
      value: null
    },

    tDiffuse: {
      value: null
    },

    textureMatrix: {
      value: null
    }

  },

  vertexShader: /* glsl */`
		uniform mat4 textureMatrix;
		varying vec4 vUv;

		#include <common>
		#include <logdepthbuf_pars_vertex>

		void main() {

			vUv = textureMatrix * vec4( position, 1.0 );

			gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );

			#include <logdepthbuf_vertex>

		}`,

  fragmentShader: /* glsl */`
		uniform vec3 color;
		uniform sampler2D tDiffuse;
		varying vec4 vUv;

		#include <logdepthbuf_pars_fragment>

		float blendOverlay( float base, float blend ) {

			return( base < 0.5 ? ( 2.0 * base * blend ) : ( 1.0 - 2.0 * ( 1.0 - base ) * ( 1.0 - blend ) ) );

		}

		vec3 blendOverlay( vec3 base, vec3 blend ) {

			return vec3( blendOverlay( base.r, blend.r ), blendOverlay( base.g, blend.g ), blendOverlay( base.b, blend.b ) );

		}

		void main() {

			#include <logdepthbuf_fragment>

			vec4 base = texture2DProj( tDiffuse, vUv );
			gl_FragColor = vec4( blendOverlay( base.rgb, color ), 1.0 );

		}`
}

export { Reflector }
